Brush mounting for electric motors



May 11 1926.

R. R. SHAY BRUSH MOUNTING FOR ELECTRIC MOTORS Fild Jan. 26, 1925 ETE- 1 MM ATTY'S INVENTDR KaZp/Z Z. J/my Patented May 11, 1926.

UNITED srares raiser caries.

RALPH n. SHAY, or onroaeo, iLLinors,

AtSSIGNOE T CHICAGO APPARATUS CQM- IPANY, OF CHICAGO, ILLINOIS, A CORPORATEON (3F ILLINGIS.

BRUSH IEOUNTENG FOR ELECTRIC MOTORS.

Application filed January This invention relates generally to electric motors and in particular to a motor b ush contact mounting.

In small motors especially of the toy or of the laboratory demonstration ty e, the brush employed usually is, a projecting strip of spring metal which bears lightly on the commutator. The pressure from the strip is. subject to variation and by its construction is easily displaced from a proper operating pressure by flexure of the brush or by mechanical derangement of the mounted end. Especially in student laboratory apparatus the derangement of the brush seriously affects the correct operation of the motor. This, of course, is detrimental to the purpose for which the apparatus is used. The apparatus should properly be dispensed to the student in correct working order and it necessarily takes much time of the instructor in charge to adjust the brushes or to instruct the student in the matter before the principles of the device have become impressed upon the student.

The'object of this invention is to provide a brush of a type which is not subject to the disadvantages above setforth and in particular one which is. quickly adjustable when necessary.

A further object is to provide a brush mounting which permits a very slight change in contact pressure from a considerable motion of the adjusting part.

A. still further object is to provide a brush construction which permits of successive variations in contact pressure while the motor is running, thus enabling the effect of contact pressure to be easily demonstrated to the student as a part of his experiment.

In the drawings, I have illustrated a common type of laboratory apparatus employed for demonstrating motor principles in which- Figure 1 shows a plan view of the apparatus.

Fig. 2 shows the apparatus in front elevation.

Fig. 3 shows a detail of the brush mounting, and

Fig. 4 shows a cross section of the brush mounting along the line 4.-4- of Fig. 3.

The device consists of a base 5 upon which a bracket member 6 supports a vertical shaft 26, 1925. Serial No. 4,673.

7 freely pivoted in upper and lower bearings 8 and 9 of the bracket. An electromagnetic armature 10 is carried on the shaft with a commutator ll therefor. Grooved blocks 12 and13 on the base 5 are pivoted at the far end as shown at 1st and 15. Permanent magnets 16 and 17 are carried in grooves 18 of the blocks, a set screw 19 being employed to hold them fixed therein. The magnets are thus slidable and reversible in the blocks, and the blocks being pivoted permit motion of the magnets to and from the armature to vary the conditions experimentally under which the motor may be made to operate.

Upon the bracket 6 an insulating plate 20 is provided coaxially pivoted with the shaft 7 and'angularly adjustable in a horizontal plane with respect to the bracket member 6, clamping screw 21 permitting this adjustment..-

[at-diametrically opposite points on the pivoted plate 20, vertical shafts or brush carriers 22 and 23 project downwardly parallel to the shaft 7, terminating in a plane near the lower portion of the commutator. Binding posts'2 and 25 are provided at thetop of the plate 20 for electrical connection to the brush carrying shafts, to which posts battery wires 26 and 27 may be connected for running the motor.

Each of shafts 22 and carries a brush 28 or 29 which makes contact with the commutator 11. The mounting of the brushes is best illustrated in detail in Figs; 3 and 1- wherein the brush 29 is a strip of suitable leaf spring metal. The shaft has av ring groove 30 therein in which a split ring 81 is placed forming a shoulder thereon. Upon this shoulder rests the pivoted end of the brush. The end 32 of the brush strip 29 is circularly bent to fit about the shaft 23. By this construction the brush is freely pivoted on the shaft 23 for motion in a horizontal plane. A second member is provided which is frictionally pivoted to the same shaft. A yielding connecting means is placed between the two pivoted members to effect the ad justability of the one by the other. The frictional engagement is made by means of a knurled split collar 33 which can be sprung to fit upon the shaft to provide a proper frictional engagement thereon. A

light coiled spring 34 surrounding the shaft between the brush and the ring has one end passing through the collar 33 and. the other end 36 secured to .the brush 29 as by a solder spot 37.

In such an apparatus. the. brushes may be moved pivotally on their carrying shafts without touching the brush, thus eliminating any danger of bending oiwdisplacing them mechanically. By rotating the collar 33 motion is transmitted yieldingly to the brush through the spring 34. By turning the collar 33 so as. to tighten the spring the brush 29 will be pressed .the .harder against the commutator 11. A considerable turning of the collar ispermitted with only slight change in contact pressure of the brush on the commutator, the amount of motion of the collar, ofeourse, being .regulated by the number of coils in "the spring 34.

lVhen embodied in astudent laboratory apparatus of the type herein disclosed the ability to effect a change in pressure by.- mo-. tion of the collar 33 permits regular angular displacements of the collar 33 with a corresponding change in the pressure of the brush upon the commutator. In conducting experiments with the device, the efl'ect of these successive displacements of the adjusting ring may be determined by'the student to demonstrate the effect of frictional and electrical resistance of the brush uponthe operation of the motor. Furthermore, the brush is readily adjusted to the desired position without the necessity of touching the brush, which is conducive to the brush being always inoperative condition. By the. addition of the spring 34 to the prior constructions, the necessity for using a resilient strip for the brush disappears and it is to be understood that a" rigid arm adapted tomake contact with thecommutator may be provided, if desired, thus further limitingthe danger of injury to the brush.

It is thus obvious that I have provided a suitable brush mounting for motors, and that the invention is not limited to laboratory apparatus, but may be applied in other fields Where such a mounting will be desired.

I claim as my invention:

1. A brush construction for an electric motor. having a commutator comprising, in combination, an arm parallel to the axis of the commutator, a brush loosely and. pivotally mounted on said arm, a spring-clan'ip member pivotally mounted on said arm hav ing a frictional engagement therewith. for digital adjustment, and a coiled spring about the arm having the ends fixed with said two rotatable members. the spring being insufficient in strength to overcome the frictional engagen'ient of the spring-clamp member with said arm.

2. A brush construction for an electrical motor having a commutator comprising, in combination, a fixed pivot shaft parallel to the axis of the motor commutator, a strip of metal pivoted atone end on said shaft and adapted adjacent the other end to make contact with saidcommutator, a coiled spring aboutsaid shaft having one end'secured to the strip of metal, a digitally adjustable re silent clamping means rotatable with frictional en gagementon said pivot shaft to move the brush, said spring having its other end socured to said rotatable means to effectitransmission of motion or pressure to the strip o'l' .material whereby to va-ryits relation to said commutator by motion 'of'said rotatable means.

A brush construction for a motor having a commutator comprising, in combination, a pivot shaft parallel to the axis of the commutator, an arm pivoted on said shaft to make contact" with the comn'iutator, a coiled spring about said shaft, a digitally adjustable resilient split collar having frictional engagement with said shaft, said spring having its ends positioned to move with the arm and with said collar in their pivotal motion whereby motion of the collar is yieldably transmitted as motion or pressure to the arm.

' In testimony whereof, I have hereunto atfixed my signature.

RALPH R. SHAY. 

